Conventionally, zoom lenses of the two group type, constituted by a first lens group having a negative refractive power and a second lens group having a positive refractive power in this order from an object side, that change magnification by moving the first lens group and the second lens group in the direction of the optical axis, are known as zoom lenses having variable magnification ratios of approximately 2.5× and wide angles. This type of zoom lens is favorably employed for miniature video cameras and the like.
For example, U.S. Pat. No. 5,877,901 discloses a zoom lens of the two group type having four lenses in a first lens group (Example 5). The first lens group of this zoom lens has a negative lens (a lens having a negative refractive power), a negative lens, a negative lens, and a positive lens (a lens having a positive refractive power), in this order from the object side.
U.S. Pat. No. 6,940,655 discloses a zoom lens of the two group type having four lenses in a first lens group (Example 1). The first lens group of this zoom lens has a negative lens, a positive lens, a negative lens, and a positive lens, in this order from the object side.
U.S. Pat. No. 7,050,240 discloses a zoom lens of the two group type having four lenses in a first lens group and four lenses in a second lens group (Example 2). The first lens group of this zoom lens has a negative lens, a negative lens, a negative lens, and a positive lens, in this order from the object side. The second lens group of this zoom lens has a positive lens, a positive lens, a negative lens, and a positive lens, in this order from the object side.
U.S. Pat. No. 6,169,635 discloses a zoom lens of the two group type having four lenses in a first lens group and four lenses in a second lens group (Example 4). The first lens group of this zoom lens has a negative lens, a positive lens, a negative lens, and a positive lens, in this order from the object side. The second lens group of this zoom lens has a positive lens, a positive lens, a negative lens, and a positive lens, in this order from the object side.
Japanese Unexamined Patent Publication Nos. 2006-276430 and 2008-065051 also disclose zoom lenses having lens configurations similar to that disclosed in U.S. Pat. No. 7,050,240 as Example 1 and Example 4, respectively.
Japanese Unexamined Patent Publication Nos. 2002-277737 and U.S. Patent Application Publication No. 20080106801 also disclose zoom lenses having lens configurations similar to that disclosed in U.S. Pat. No. 5,877,901 as Example 1 and Example 1, respectively.